1. Field of the Invention
The present invention relates to an optical disc including a feature of protection against illegal or impermissible copying of data from the optical disc, and a method of recording data into the optical disc.
2. Description of Related Art
The disc drive compatible with recordable optical discs of phase-change type such as so-called DVD-RAM disc, etc. records AV data including video signal, audio signal, etc. through encryption of the AV data. To reproduce the AV data, the AV data read from the optical disc is decrypted to provide the original video and audio signals.
For example, the optical disc drive shown in FIG. 1 is adapted to encrypt, using a disc key to encrypt an entire AV data for recording into an optical disc, a sector key to encrypt the AV data for each program. The AV data is encrypted for each program using the encrypted disc key and recorded along with the disc key and encrypted sector key into the optical disc.
When reproducing the AV data, the optical disc drive uses the disc key and encrypted sector key to decrypt the sector key, and the decrypted sector key to decrypt the encrypted AV data.
Normally, such encryption and decryption are not laid open in detail to the public from the standpoint of the prevention of illegal or impermissible copy. Therefore, the ordinary user cannot illegally copy AV data so long as he or she does not know how an IC (integrated circuit) to encrypt data in the optical disc drive is configured.
Concerning the above-mentioned phase-change type optical disc, when a same data is repeatedly recorded in a same place in the disc, recording marks and their periphery are deteriorated due to a thermal stress and others. Thus, the optical disc is limited in its capability of repeatedly recording data in it as the case may be. To avoid recording sync signals having a same signal pattern in a same place in the optical disc, it has been proposed to shift the recording position at random, namely, to adopt the Start Position Shift (SPS) method.
However, if the configuration of the IC used in the optical disc drive to encrypt data is known to a person who would try an illegal copying, a method of decrypting the encrypted data will also be known to him, so an AV data recorded in an original optical disc may possibly be copied into another optical disc.
Further, along with the increasingly greater interest in the security such as copy protection, it has been more and more demanded to prevent illegal copy by recording a unique disc identification (ID) information into each optical disc.
It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art and meet the requirements for illegal copy preventing by providing an optical disc having an ID number written therein by the SPS method to make it impossible to reproduce a data illegally copied from the optical disc, and a method of recording data into the optical disc.
According to the present invention, there is provided an optical disc having a plurality of sectors each including a head area and recording area, in which a position where a predetermined amount of data is recorded in the recording area of each sector provides an ID information for the optical disc.
According to the present invention, there is provided an optical disc having a plurality of segments each including a header area and recording area, in which a position where a predetermined amount of data is recorded in the recording area of each segment provides an ID information for the optical disc.
According to the present invention, there is provided a method of recording data into an optical disc having a plurality of sectors each including a header area and recording area, in which a position where a predetermined amount of data is recorded in the recording area of each sector provides an ID information, comprising the steps of:
firstly encrypting, using the ID information in the optical disc, a disc key to encrypt a user data included in the predetermined amount of data;
secondly encrypting, using the firstly encrypted disc key, a sector key to encrypt the user data for each program; and
thirdly encrypting the user data using the secondly encrypted sector key, thereby recording the encrypted user data into the recording area of the optical disc.
According to the present invention, there is provided a method of recording data into an optical disc having a plurality of segments each including a header area and recording area, which a position where a predetermined amount of data is recorded in the recording area of each segment provides an ID information, comprising the steps of:
firstly encrypting, using the ID information in the optical disc, a disc key to encrypt a user data included in the predetermined amount of data;
secondly encrypting, using the firstly encrypted disc key, a sector key to encrypt the user data for each program; and
thirdly encrypting the user data using the secondly encrypted sector, thereby recording the encrypted user data into the recording area of the optical disc.
In the method of recoding data into the optical disc according to the present invention, the ID information recorded in the optical disc is used to firstly encrypt a disc key to encrypt a user data included in a predetermined amount of data, the firstly encrypted disc key is used to secondly encrypt the data for each program, and the secondly encrypted sector key is used to thirdly encrypt the user data for each program, thus encrypting optical discs differently from one to another.